Strange problem?

I have a Spector Euro 5.Fantastic Bass.I have a strange problem with the Strings.Say I play a note on the D String ninth Fret.My E String rings out as well.This happens with certain notes on different Strings but mainly the E and A Strings will ring out.I have Spector Strings on the Bass which are all tapered except the G String.Could Tapered Strings cause this problem.Any other Bass I have used never had this problem.This is my first time having Tapered Strings.